The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Sydney man recalls finding dead fiancee

When Niraj Dave first got home after a night shift, he says he didn't initially notice his fiancee's body beside the bed.

"I asked, 'Purvi, Purvi where are you?' ... I thought maybe she has gone down for laundry."

But when he took a second look into their bedroom he saw a hand on the floor.

"I thought what is she doing on the floor. So I went to see and I saw her face was black."

Struggling through tears, Mr Dave's voice cracked in the Supreme Court on Tuesday as he described talking to his unresponsive 28-year-old fiancee Purvi Joshi on the floor of their Kyeemagh apartment in southern Sydney.